1. Field of the Disclosure
The present invention relates in general to roofing and, in particular, to a system, method and apparatus for thermal energy management in a roof by reversible sorption and desorption of moisture.
2. Description of the Related Art
Typical residential roofs in the North America have bitumen-based roofing materials that provide satisfactory water shedding, long term durability and have aesthetic appeal. Most asphaltic roofing materials are colored in traditional dark earth tones. These colors absorb significant amounts of solar heat during hot summer times, which penetrates through the roof deck, attic and ceiling into the house. The heat penetration increases the need for cooling energy for the indoor comfort of residence occupants.
On the other hand, these types of roofing products usually have good thermal emittance and low thermal mass. These properties allow them to quickly re-radiate and lose solar heat during the night. This results in the so-called “super cooling” effect that may increase the heating energy need to maintain indoor temperatures during the night. This issue is particularly problematic for cold to moderate climate regions, and for seasons where the day and night temperature differences are significant, such as in the spring or fall seasons.
Therefore, it would be advantageous to have a roofing system that can store or manage the solar heat during the day, and then release that heat into the house during the night to improve the energy efficiency of the house. It would be a further advantage to have such a system that is compatible with current asphaltic shingle aesthetics, and can be readily applied with existing roofing techniques and construction practices.
Some asphaltic shingles have improved solar reflectance that reduces the absorption of solar heat. Although such products lower cooling energy costs, particularly in warmer climates, they are not designed for managing solar heat during the night or for significant seasonal changes. In colder climates, these products can have heating penalties due to the loss of solar heat. This is also true when radiant barriers are used to reduce solar heat flux into the attic. Radiant barriers do not capture or manage solar heat.
Other conventional solutions include ventilated decks and ventilation systems that reduce heat flux into the attic via air flows to expel heat. Again, these systems do not store or manage solar heat for the later cooler times of day. Therefore, it would be advantageous to have a roofing material/system that can store or manage the solar heat during the day time and then release back into the house during the night time to optimize whole building energy efficiency. It is further advantageous to have such a material/system that will not affect current asphaltic shingle aesthetic values or can be applied easily with current known roofing technique or construction practices.